Bond Polarity and Molecular Polarity Worksheet | PDF - Free Printable

Let's solve each part of the "Worksheet - Polarity of Bonds" step by step with detailed explanations.

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1. Determine the type of bond and show polarity (if applicable)

We use electronegativity differences to determine bond type:

- ΔEN > ~3.0: Ionic
- ΔEN = 0.4–3.0: Polar covalent (more polar as ΔEN increases)
- ΔEN < 0.4: Non-polar covalent
- Slightly polar covalent is typically ΔEN ≈ 0.4–1.0

Use electronegativity values (Pauling scale):
- Ca: 1.0, Cl: 3.0 → ΔEN = 2.0
- C: 2.5, S: 2.5 → ΔEN = 0.0
- Mg: 1.3, F: 4.0 → ΔEN = 2.7
- N: 3.0, O: 3.5 → ΔEN = 0.5
- H: 2.1, O: 3.5 → ΔEN = 1.4
- S: 2.5, O: 3.5 → ΔEN = 1.0

#### a. Ca and Cl
- ΔEN = 3.0 – 1.0 = 2.0
- Ionic bond (large difference, metal + nonmetal)
- Arrow: Not needed (ionic)

✔ Answer: Ionic

#### b. C and S
- ΔEN = 2.5 – 2.5 = 0.0
- Non-polar covalent

✔ Answer: Non-polar covalent

#### c. Mg and F
- ΔEN = 4.0 – 1.3 = 2.7
- Ionic bond (Mg is metal, F is highly electronegative nonmetal)

✔ Answer: Ionic

#### d. N and O
- ΔEN = 3.5 – 3.0 = 0.5
- Polar covalent
- Arrow from N to O (O is more electronegative)

✔ Answer: Polar covalent, arrow: N → O

#### e. H and O
- ΔEN = 3.5 – 2.1 = 1.4
- Polar covalent
- Arrow from H to O (O is more electronegative)

✔ Answer: Polar covalent, arrow: H → O

#### f. S and O
- ΔEN = 3.5 – 2.5 = 1.0
- Polar covalent
- Arrow from S to O (O is more electronegative)

✔ Answer: Polar covalent, arrow: S → O

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2. Arrange covalent bonds in order of polarity (most polar first)

All are covalent, so we compare ΔEN:

| Bond | Electronegativity | ΔEN |
|------|-------------------|-----|
| H–Cl | H=2.1, Cl=3.0 | 0.9 |
| H–C | H=2.1, C=2.5 | 0.4 |
| H–F | H=2.1, F=4.0 | 1.9 ← most polar |
| H–O | H=2.1, O=3.5 | 1.4 |
| H–H | H=2.1, H=2.1 | 0.0 |
| S–Cl | S=2.5, Cl=3.0 | 0.5 |

Order of polarity (most to least):

1. H–F (ΔEN = 1.9) → Most polar
2. H–O (ΔEN = 1.4)
3. H–Cl (ΔEN = 0.9)
4. S–Cl (ΔEN = 0.5)
5. H–C (ΔEN = 0.4)
6. H–H (ΔEN = 0.0) → Nonpolar

Now draw arrows for polar bonds:
- H–F: H → F
- H–O: H → O
- H–Cl: H → Cl
- S–Cl: S → Cl
- H–C: H → C (slight)
- H–H: no arrow

✔ Final Order (most to least polar):
1. H–F
2. H–O
3. H–Cl
4. S–Cl
5. H–C
6. H–H

With arrows:
- H→F, H→O, H→Cl, S→Cl, H→C, H–H (no arrow)

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3. Analyze molecules: bond type, electron geometry, molecular geometry, and polarity

We'll go one by one.

| Molecule | Type of bonds | Electron Group Geometry | Molecular Geometry | Molecular Polarity |
|---------|---------------|--------------------------|--------------------|---------------------|
| PCl₃ | Polar covalent | Trigonal pyramidal | Trigonal pyramidal | Polar |
| NH₃ | Polar covalent | Trigonal pyramidal | Trigonal pyramidal | Polar |
| H₂O | Polar covalent | Bent | Bent | Polar |
| CaO | Ionic | — | — | Ionic compound |
| H₂S | Polar covalent | Bent | Bent | Polar |
| HCl | Polar covalent | Linear | Linear | Polar |
| Br₂ | Non-polar covalent | Linear | Linear | Non-polar |
| HCN | Polar covalent | Linear | Linear | Polar |
| NI₃ | Polar covalent | Trigonal pyramidal | Trigonal pyramidal | Polar |

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Detailed Analysis for Each Molecule

#### PCl₃
- Central atom: P
- Valence electrons: P has 5, each Cl contributes 1 → 5 + 3(1) = 8 → 3 bonding pairs, 1 lone pair
- Electron group geometry: Trigonal pyramidal (4 electron groups: 3 bonds, 1 lone pair)
- Molecular geometry: Trigonal pyramidal
- P–Cl bonds are polar (P: 2.1, Cl: 3.0 → ΔEN = 0.9)
- Asymmetric shape → Polar molecule

✔ Type of bonds: Polar covalent
✔ Electron group geometry: Tetrahedral
✔ Molecular geometry: Trigonal pyramidal
✔ Molecular polarity: Polar

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#### NH₃
- N central, 3 H, 1 lone pair
- Electron groups: 4 → tetrahedral electron geometry
- Molecular shape: Trigonal pyramidal
- N–H bonds polar (ΔEN = 3.0 – 2.1 = 0.9)
- Asymmetric → Polar

✔ Type of bonds: Polar covalent
✔ Electron group geometry: Tetrahedral
✔ Molecular geometry: Trigonal pyramidal
✔ Molecular polarity: Polar

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#### H₂O
- O central, 2 H, 2 lone pairs
- Electron groups: 4 → tetrahedral
- Molecular shape: Bent
- O–H bonds polar (ΔEN = 1.4)
- Bent shape → Polar

✔ Type of bonds: Polar covalent
✔ Electron group geometry: Tetrahedral
✔ Molecular geometry: Bent
✔ Molecular polarity: Polar

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#### CaO
- Calcium oxide: Metal (Ca) + Nonmetal (O)
- Ionic bond
- No molecular shape or electron geometry (ionic crystal lattice)
- Not a molecule, but an ionic compound

✔ Type of bonds: Ionic
✔ Electron group geometry: —
✔ Molecular geometry: —
✔ Molecular polarity: Ionic compound (not applicable)

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#### H₂S
- S central, 2 H, 2 lone pairs
- Electron geometry: Tetrahedral
- Molecular geometry: Bent
- S–H bonds: polar (S: 2.5, H: 2.1 → ΔEN = 0.4)
- Bent shape → Polar

✔ Type of bonds: Polar covalent
✔ Electron group geometry: Tetrahedral
✔ Molecular geometry: Bent
✔ Molecular polarity: Polar

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#### HCl
- Diatomic molecule
- Bond: H–Cl, polar covalent (ΔEN = 0.9)
- Shape: Linear
- Dipole moment: H→Cl → Polar molecule

✔ Type of bonds: Polar covalent
✔ Electron group geometry: Linear
✔ Molecular geometry: Linear
✔ Molecular polarity: Polar

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#### Br₂
- Diatomic, same atoms
- ΔEN = 0 → Non-polar covalent
- Symmetric → Non-polar

✔ Type of bonds: Non-polar covalent
✔ Electron group geometry: Linear
✔ Molecular geometry: Linear
✔ Molecular polarity: Non-polar

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#### HCN
- H–C≡N
- Linear molecule
- C–H: slightly polar (ΔEN = 0.4), C≡N: very polar (C: 2.5, N: 3.0 → ΔEN = 0.5)
- But linear and dipole moments do not cancel? Let’s see:
- H–C bond: δ⁺ on H, δ⁻ on C
- C≡N: δ⁺ on C, δ⁻ on N
- Net dipole from H to N → Polar molecule

✔ Type of bonds: Polar covalent (C–H, C≡N)
✔ Electron group geometry: Linear
✔ Molecular geometry: Linear
✔ Molecular polarity: Polar

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#### NI₃
- Nitrogen central, bonded to 3 I atoms
- N has 5 valence electrons, each I provides 1 → 3 bonds, 1 lone pair
- Electron groups: 4 → tetrahedral electron geometry
- Molecular geometry: Trigonal pyramidal
- N–I bonds: N (3.0), I (2.5) → ΔEN = 0.5 → Polar covalent
- Asymmetric → Polar

✔ Type of bonds: Polar covalent
✔ Electron group geometry: Tetrahedral
✔ Molecular geometry: Trigonal pyramidal
✔ Molecular polarity: Polar

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✔ Final Answer Table:

| Molecule | Type of bonds | Electron Group Geometry | Molecular Geometry | Molecular Polarity |
|--------|----------------|----------------------------|---------------------|---------------------|
| PCl₃ | Polar covalent | Tetrahedral | Trigonal pyramidal | Polar |
| NH₃ | Polar covalent | Tetrahedral | Trigonal pyramidal | Polar |
| H₂O | Polar covalent | Tetrahedral | Bent | Polar |
| CaO | Ionic | — | — | Ionic compound |
| H₂S | Polar covalent | Tetrahedral | Bent | Polar |
| HCl | Polar covalent | Linear | Linear | Polar |
| Br₂ | Non-polar covalent | Linear | Linear | Non-polar |
| HCN | Polar covalent | Linear | Linear | Polar |
| NI₃ | Polar covalent | Tetrahedral | Trigonal pyramidal | Polar |

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Summary of Key Concepts:

- Bond polarity depends on electronegativity difference.
- Molecular polarity depends on both bond polarity and molecular geometry.
- Even if bonds are polar, if the molecule is symmetric (e.g., CO₂), it may be non-polar overall.
- In this worksheet, all molecules with asymmetric shapes and polar bonds are polar.

Let me know if you'd like diagrams (arrows, shapes) drawn!